json-parser

Overview

The json-parser node converts between JSON strings and JavaScript objects. Use it to parse incoming JSON text from APIs, serial devices, and files into usable objects, or to stringify objects back into JSON for transmission and storage.

Properties

Actions

Input:  msg.payload.data = '{"temp":23.5}'
Output: msg.payload.data = { temp: 23.5 }

Input:  msg.payload.data = { temp: 23.5 }
Output: msg.payload.data = '{"temp":23.5}'

Example: Parse API Response

Parse a JSON string received from an HTTP request into a usable object.

// json-parser node configuration
{
  "action": "parse",
  "property": "payload",
  "target": "payload"
}

// Input from HTTP request node:
{
  "payload": {
    "data": "{\"status\":\"ok\",\"temperature\":23.5,\"humidity\":65}"
  }
}

// Output after parsing:
{
  "payload": {
    "data": {
      "status": "ok",
      "temperature": 23.5,
      "humidity": 65
    }
  }
}

// Flow: [http-request] → [json-parser] → [switch on status]

Example: Parse Serial JSON Data

Parse JSON strings received from an Arduino over serial into structured data.

// json-parser node configuration
{
  "action": "parse"
}

// Arduino sends: {"temp":23.5,"humidity":65,"sensor":"dht22"}
// serial-in receives as string in msg.payload.data

// After json-parser:
{
  "payload": {
    "data": {
      "temp": 23.5,
      "humidity": 65,
      "sensor": "dht22"
    }
  }
}

// Flow: [serial-in] → [json-parser] → [set node] → [dashboard]

Example: Stringify for MQTT Publish

Convert an object to a JSON string before publishing to an MQTT topic.

// json-parser node configuration
{
  "action": "stringify"
}

// Input from function node:
{
  "payload": {
    "data": {
      "device": "sensor-01",
      "temperature": 23.5,
      "timestamp": 1700000000
    }
  }
}

// Output after stringify:
{
  "payload": {
    "data": "{\"device\":\"sensor-01\",\"temperature\":23.5,\"timestamp\":1700000000}"
  }
}

// Flow: [function build obj] → [json-parser stringify] → [mqtt-out]

Common Use Cases